The need to move large volumes of highly abrasive materials, such as coal, grain, sand, and various waste products, places great demands on the piping systems through which they are conveyed. Excessive wear is a common problem, especially evident in the sections of pipe which change the direction of flow of the abrasive material.
As is known, upon a change in direction of flow of a fluid containing abrasive particles, the wall facing the oncoming stream is subjected to a continuous bombardment of such particles. The result is that the outer bends of the pipes in these transport systems are rapidly worn down and the fittings must be replaced or patched at frequent intervals to prevent leakage of dust, contamination of the surrounding atmosphere, et cetera, so as to avoid health hazards as well as explosive situations. The down time and other costs accrued in the need to continually make such repairs represent a substantial economic loss.
In conveying abrasive materials such as, for example, coal in a slurry, curved sections of pipe may be made of a highly durable material in order to withstand abrasive contact with the material being conveyed therethrough. For this purpose, it is a well known practice to provide pipe elbows with an abrasion resistant inner lining to increase the wear life of the pipe elbow. Due to their excellent wear characteristics, ceramic brick and ceramic materials have become increasingly popular for use in lining pipe casings subjected to high abrasive wear conditions.
One known method for providing a ceramic inner wear liner for a pipe fitting involves bricking the inner surface of the pipe elbow casing with a plurality of ceramic wear bricks. The wear bricks are fitted into position inside the casing in a series of rings in a keystone arrangement along the length of the elbow. Unfortunately, it is extremely expensive to provide a ceramic inner lining for a pipe elbow in this fashion because each brick is differently sized and shaped according to its angular location about the center line of the pipe elbow. Nevertheless, the use of ceramic wear bricks to totally line the inner surface of a pipe elbow results in a pipe elbow having an improved wear life.
In U.S. Pat. No. 1,246,189 an albow construction is described which consists of two separate semi-cylindrical sections with the medial portion of one section being enlarged to accommodate a recess into which lining blocks are inserted.
Another approach is illustrated in U.S. Pat. No. 3,977,730 where an impact plate is fixed to the outside surface of the outer bend of the pipe elbow.
In U.S. Pat. No. 3,794,359, a pipe elbow fabricated entirely from non-metallic materials is described. The elbow consists of a pair of wear plates of ceramic material having a semi-circular shape and assembled circumferentially in opposing spaced relationship to each other. A resinous grout is disposed in the circumferential space between the opposed wear plates and a fiberglass reinforced resin provides a cover over the wear plates and grout.
However, in each of these pipe elbows there remains much room for improvement in wear resistance, ease of manufacturability and ease of repair. It is an object of the present invention to provide an abrasion resistant bend construction for abrasive material conveying pipelines which overcomes problems of cost of manufacture, high wear, and expanse of maintenance.